1. Field of the Invention
The present invention relates to novel gas sensors that may be used in conjunction with boilers, furnaces, or other combustors.
2. Discussion of Related Art
In numerous industrial environments, a hydrocarbon fuel is burned in a combustor (e.g., a boiler or furnace) to produce heat to raise the temperature of a fluid. The fluid may, for example, be water which is heated to generate steam to drive a turbine generator that provides power. Such industrial combustors typically employ an array of many individual burner elements to combust the fuel. In these combustors, various post-flame combustion control systems, such as overfire air, staging air, reburning systems, and selective non-catalytic reduction systems, can be employed in the post-flame zone to enhance the efficiency of the combustor. For the combustor to operate efficiently and to produce an acceptably complete combustion having byproducts that fall within the limits imposed by environmental regulations and design constraints, all of the individual burners should be operating cleanly and efficiently, and all post-flame combustion control systems should be properly balanced and adjusted.
Emissions of unburned carbon, nitrous oxides, carbon monoxide or other byproducts commonly are monitored to ensure compliance with environmental regulations. The monitoring of emissions heretofore has been done, by necessity, on the aggregate emissions from the combustor (i.e., the entire burner array--taken as a whole). Some emissions, such as the concentration of gaseous combustibles in hot flue gases, are difficult and/or expensive to monitor on-line and continuously. These emissions are typically measured on a periodic or occasional basis. When a particular combustion byproduct is found to be produced at unacceptably high concentrations, the combustor should be adjusted to restore proper operations. However, measurement of aggregate emissions, or measurement of emissions on a periodic or occasional basis, provides little, if any, useful information regarding what particular combustor parameters should be changed to effect such an adjustment.